use std::io; // prelude
use rand::Rng; // trait
use std::cmp::Ordering;

fn main() {
    println!("猜数!");

    let secret_number = rand::thread_rng().gen_range(1,101);

    println!("神秘数字是：{}", secret_number);

    loop {
        println!("猜一个数");

        let foo = 1;
        let bar = foo; // immutable
        println!("bar: {}",bar);

        let mut guess = String::new();

        io::stdin().read_line(&mut guess)
        .expect("无法读取行");

        println!("你猜测的数是：{}", guess);

        // shadow 允许同名，隐藏机制
        // let guess: u32 = guess.trim().parse().expect("你猜测的不是整数");
        let guess: u32 = match guess.trim().parse() {
            Ok(num) => num,
            Err(_) => {
                println!("你猜测的不是整数!");
                continue;
            }
        };

        match guess.cmp(&secret_number) {
            Ordering::Less => println!("Too small!"),
            Ordering::Greater => println!("Too big!"),
            Ordering::Equal => {
                println!("You Win!");
                break;
            }
        };
    }

}

